Total tripe. 11 l/min @35C temp rise. At 5C mains temp, it will deliver about 9 to 9.5 litres/min at 45C (shower temp), that is just the hot water flow. 9 litres/min is more than fine, and "nowhere" near marginal, and about 2 l/min over recommendations.
Phew....
I left my message, went down the pub, watched a bit of cricket, came back to the computer and find all your replies. Thanks a lot certainly a quicker response than the Vaillant helpline.
Anyway, firstly I admit that I'm not a plumber (nor a "cheapo landlord")but am a reasonably seasoned diy-er. I used to do bits of plumbing until I had to get a corgi to do everything and I used to do electrics before I had to ask the building inspector how to wire a plug.
Anyway, I left this system to a qualified corgi plumber(he said) who fully assessed the relevant dhw and ch requirements (I even have a bit of paper to prove it) to allow for a family of four or five, requiring hw for shower, bath and basin, sink, dw and wm. He concluded the turbomax 828 was ok with over 100000 btu and need for showers made combi best. The fact that he had a cheap one left over from the last job would not have been on his mind.
The cold water incoming flow is ok/very good although it does have appliances etc teed off it so we could work on rearranging and upgrade pipe to 22mm. Dedicated feed for boiler back to the stop c*ck would be easy.
Despite what Dr Drivel says I cannot be convinced that a combi is right. Even a high flow rate one (whatever that is?)
I didn't ask to have the bath removed nor do I want all the hassle of taking a new gas supply three floors up the house together with flue etc (not outside wall). If I'm not keen on one combi I'm hardly likely to want two am I?
No surely the best bet is new system boiler wall hung where the existing is (with improved pipework) and some sort of storage as much as possible (200l) (megaflow/vantage etc)to give equal pressure all round the house utilising existing pipework already there. In other words admit we got it wrong on the spec first time!
Anyone want a nearly new Vaillant 828 combi (Highbury north London) otherwise its ebay
If you read what you just wrote, you will realise that you have written tripe.
If 45 degrees is shower temp, then it would be the *only* flow - you wouldn't be adding cold to it if that is the usage temperature.
9 litres/min is piss poor and not a great deal more than an electric shower.To top it all, you are advocating that the poor students make do with this rather than being able to have a bath.
That's where we came in. It's inadequate and you are trying to make a case that it is adequate. Nonsense.
The film has been running for a couple of hours and it's almost time for the ice cream lady to come round.
..let's see what his conclusions are.....
Nonsense. The recommended is 7 to 7.5 litres. 9 to 10 is more than adequate. It is the strong pressure on the skin that people want, not masses of needless wasteful flow. That is the worst case example, while right now at about 18C mains water temp it will deliver far more.
Tripe. Electric are piss poor; 9 l/min is about the best you will get and they cost.
A normal 11 l/min combi delivers an excellent shower all year around.
Sorry Andy but unless there's a bit of physics missing me, for the same temperature a 28kW combi is going to deliver 3 times the flow of a
9.5kW electric shower. Three times is a lot more than "not a great deal more". My 24kW combi delivers a vastly better shower than the gravity fed Mira 8 that preceded it.
That, and many people fit tiddly little 24kW toy ones.
I'd say there's a big difference between the requirements of a family of
5 and a housefull of 5 students. In a family, there are likely to be kids needing a tub at 7pm, or older ones who can be told (with luck) to have their shower or bath in the evening to avoid clogging up the bathroom for mum and dad in the morning. With the students, you have 5 adults, all doing the same thing and without the 'pecking order' of the family, and they are all likely will want a shower or bath at exactly the same time of day.David
Recommended by whom?
Says who?
Says who?
Irrelevant. A system should always be designed for the worst case or close to it.
So if 9lpm is piss poor, why are you saying that it's OK of delivered by a combi rather than an electric shower? Do they have an attachment to dispense Holy Water or something?
If you have low enough expectations of the word "excellent"
Yes of course, but in comparison with 15-20lpm from a storage system both are limited.
Why not keep the existing combi and add a cylinder to the central heating side, as has been suggested.
That way you have the best of both worlds - unlimited trickle of instant tepid water from the combi side, and stored hot water after a little wait on the cylinder side.
A win win situation without using two combis and, if you use a heatbank rather than a mains pressure cylinder, you can DIY it and won't need an annual safety certificate on a pressurised cylinder.
Owain
Many millions throughout the world.
They are, and cope well then.
That is the best they can do at the best case scenario. In the worst case 7 at most.
That is a silly comment expected from someone who drives around a filthy diesel 4x4 with the aerodynamics of a brick. You are a mobile global warming enhancing pollution machine. Waste for the sake of waste.
That is not the point in question here. It is your "not a great deal more" electric /combi misparrison.
20 litres/min is irresponsible. People want the high pressure against the skin not volume.
What you wrote was very sensible.
The combi flowrate is clearly unsuitable for the demands.
High flowrate is what is says. Yours is 11/litres min flowrate. A high one will be 20 litres/min and above. In short about twice what you have, and will fill bath in no time, and do 2 to 3 showers simultaneously..
You didn't, but why have one with a bunch of young students - who will not clean it anyway. It only puts pressure on the DHW system.
You don't like this combi, which is a very good one, because it was misapplied.
The 828 "is" a system boiler. All you need do is not connect up the water section.
Keep an open mind, Two approaches for you. Take heed.
Rinnai have a model that can be fitted "outside", so no fluing problems. It has built-in frost protection.
Just find a suitable location, run a gas pipe, supply pipe and DHW draw-off pipe. This way if one of the DHW heating appliances is down the other still works, so less pressure on you in case of breakdowns, as always DHW somewhere in the house.
Have dedicated 22mm supplies to the combi and multi-point. The Rinnai is made in Japan and is very reliable. One of the biggest selling instant heaters in the world. Rinnai are the world's largest gas appliance maker.
What other gas appliances are there?
I would go for the Rinnai solution, as you have backup, never run out of hot water, flexible in location (even outside), no space taken up by a cylinder, cheaper, etc.
Don't be so pathetic!!! The mans is after constructive advise, not Jocko stupidity.
Which people?
Assuming that your flow rate is ok (i.e. >= 20l/m) then you have plenty of options. Although it might be worth estimating what your worst case water demand is going to be. If it exceeds the mains capacity then you are either going to need to make use of stored water (i.e. loft cistern, or mains pressure accumulator), or go for a mains upgrade.
Using the model you have to supply all hot water on an "instantaneous" basis is obviously not a good solution - it is way short of power to do that.
I would suggest that you keep the existing boiler (since it is a good one), and re-plumb things to use it mostly as a system boiler. I would probably take the DHW output from it to feed one shower or perhaps the kitchen, and then plumb everything else to be fed from the stored hot water system. (unvented / heatbank or whatever you want)
Normal people.
Ah... How would you know then?
I know that they are very different to abnormal people like yourself.
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